Thermal relay.



T. B. FRBAS.

THERMAL RELAY.

APPLICATION FILED DEG. 4, 1911.

1,111,789, Patented Sept.2l9,1914.

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4 5 Z y 5Z\H 5/0 Q50 UNITED STATES PATENT oEEIcE.

THOMAS B. FREAS, OF EA-ST ORANGE, NEW JERSEY, ASSIGNOR TO Y. WEBER &COM- PANY, 0F CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

THERMAL RELAY.

To all whom 'it may concern.:

Be it known that I, THOMAS B. FREAs, a citizen ofthe United btates,residing at East Orange, in the county of Essex and State of NewA`Jersey, have invented a 4certain new and use'ful Improvement 1n ThermalRelays, of which the following .is a specification.

My invention relates l-to thermal relays.

Generally speaking, my apparatus consists of a main vor controlledcircuit and a relay or controlling circuit, the 'relay or controllingcircuit being itself controlled preferably by a thermo responsiveswitch. l

One 4of .the objects of the invention is to provide means for procuringcertainty of-g operation of the main switch.

Another object is to provide means to prevent overheating of theresistance coil which operates the main switch. In the form illustratedmy invention is adapted for a constant temperature bath and the maincircuit energizes a lamp or other heater which is located near enough to.the thermo responsive switch to influence it. In this .specific formthe thermo responsive switch is a mercury tube adapted yto open andclose the .relay or controlling circuit, and :the heater .is located inthe same chamber as the tube so that the ,temperature ofthe chamber willdetermine whether the tube shall hold lthe relay circuit open or closed.

@ne of my objects is .to obtain a constant temperature bath which iselectrically heated and which has the characteristics above mentioned,to wit, a sure acting main 'switch and a protection against overheatingof the resistance coil by which the main switch 'is operated.

In the accompanying drawings, Figure 1 is a general wiring `diagram ofthe parts, and Fig. 2 is a detail showing the preferred form of switcharm and contacts of the heat-actuated switches.

In the controlling circuit is a thermo responsive switch consisting of amercury tube 1 containing mercury, which is at all times in electricalcontact with vthe conductor 2 provided with a fuse 3 and leading'throughA Letters Patent.

Patented Sept. 2.9, 1914. seria No. scarsi.

.of fthe air or .other medium surrounding the mercury tube causes themercury to rise .to a predetermined level. It is unnecessary to.describe ,the precise construction here, as the construction of thisswitch -is not .an essential feature of thisinvention, and the form hereshown is described in detail in my c0- pending application filed January4, 1912, Serial Number 169,344, (Case D). Furthermore thermo responsiveswitches of this general character have heretofore been shown, fas, forexample, in my issued Patents Number 999, 710, dated August l, 1911 andNum- !ber 1,024,565 dated April 30, 1912.

The needle 6 which .constitutes one of :the terminals of this thermoresponsive switch .is connected by a .conductor 7 and fuse 8 andconductor 9to one end of Va heating coil 10. Coi-l 10 surrounds a rod 11preferably hollow and composed of brass, the arrangement being such:that when :the coil is energized and zthe .resistance of the coilproducesheating, the heating and cooling of the coil will cause fthecorresponding heating and cooling of the rod with a consequent increaseand decrease in the length of the rod, thus furnishing 'motive power foroperating the switches presently to be described. The remaining end ofthe. coil is connected by a conductor 12 to a terminal block 13containing a contacter' 15, best shown in Fig. 2. Said coil is .biilar;'that is, the wire thereof is doubled .back upon itself so that the coilas a whole is fnoninductive. The result vis that sparking is ,avoidedwhen the circuit through it .is opened and hence delicate needle -pointsmight, without harm to them, be substituted for the mercury contact inthe tube -1.

The contacter 15v is a screw with a knurled. head 16 and screws .intovblock 13 and .remains in electrical contact with .conductor 12. Saidcontacter may be set lto anydesired adjustment by means ofthe lock nu-t17.

'Red A11 -above mentioned is rigidly secured at one 'end Ato astationary bracket 20. At -the other yend it .is articulately connectedto a .lever 21 which is fulcrumed upon a rod 22 rigidly secured4 to .thebracket 20. Near the point of lconnection to said lever ,the rod 22 isguided by a bracket 23. It is clear that the heating and cooling of rod11 under the action of the heating coil will produce a4 movement of thelever 21 about its fulcrum. But rods 11 and 22 are made similar to eachother and are connected to the same bracket and at the other end to thesame lever 21, hence changes in temperature of the atmosphere willaffect them both equally and therefore produce no movement of the lever.Consequently the rods compensate each other in so far as changes inatmospheric temperature are concerned.

The lever 21 is a conductor and is connected at one end by a conductor25 to the main line conductor 26. At the free end of said lever is aexible contact adapted to impinge the contact 15. It also has aninexible contact 31 adapted to impinge the contact screw 32 which isprovided with a knurled head 33 and screws into the stationary block 34.Block 34 makes electrical contact with the conductor 35 and screw 32 isset in proper position by means of lock nut 36. Under normal adjustmentthe parts are so arranged that when the lever 21 is moving toward thecontacts 15 and 32 the flexible portion.30 will engage the screw 15before the rigid portion 31 engages the screw 32. As the portion 30 isyieldable, however, it does not prevent the lever continuing itsmovement and bringing the parts 31 into engagement with the screw 32.Conversely when the lever is moving toward open position, the flexiblecontacter 30 will remain in contact for a delinite period after thecontactor 31 has left the contact 32 and continue the heating of thecoil after the switch 31, 32 which controls the controlled circuit isopen. As the elements are adjustable this period of lag may be regulatedas desired.

Conductor 35 is connected by the conductor 40 tothe heating lamp 41 orother translating device, the remaining terminal of the device beingconnected by conductor 42 to the main line conductor 5. By preference,

a condenser 45 is connected between the conductors 35 and 26 to preventsparking across the contact points 31 and 32. The adjustable tensionspring 47 constantly urges the lever 21 toward closed position, andserves to absorb any back lash that might otherwise be resent. v

A deslrable adjunct of my apparatus is -shown in the upper right cornerof Fig. 1

and consistsy of a tell-tale lamp 50a connected by a conductor 51 to themain line conductor 26 and by a conductor 50 to a hand switch 52connected by a conductor 53 to the conductor 9. This lam is for aidingin the adjustment of the n le 6 and when switch 52. is closed the lamp50 will glow the moment contact is made between the needle and themercury and will cease to glow the moment contact is broken. Theoperator may thus readily determine the exact moment when the contact ismade and broken. Under normal operating conditions after the needle, 6had been adjusted the switch 52 will remain open.

To facilitate an explanation of the operatien of the parts, let it beassumed that mercury tube 1 is located within and subject to thetemperature of a constant temperature bath. Let it be assumed also thatheat for the bath is furnished by the lamp 41. lVheu the bath is coldthe mercury in tube 1 will be down out of contact with needle 6, and thecircuit through the heating coil 10 will therefore be broken at thispoint. The rod 11 will be contracted and will hold the lever 21 inclosed position. start the operation of the bath thepperator closes themain switch thus causing the lamp 41 to be energized and raise the'`tcmperature of ythe bath. temperature has been raised .to apredetermined degree the mercury in tube 1 will contact the needle 6 andthus establish electrical connection between the conductors 2 and 7.Current will now pass through the resistance coil 10 and heat it, thusheating rod 1l and causing it to elongate and move the lever 21 towardopen position. Contact 32 is so adjusted that the contactor 31 willleave it almost immediately after coil 10 begins to heat.

As soon as the bathl When it is desired to This breaks the circuitthrough the heater i 41 and consequently shuts eff the supply of heat tothe bath. But for a period the length of which may be regulated, thecontactor 30 remains in engagement with its 4contact 3l and thuscontinues the heating of the coil. It is here that the advantage of myapparatus becomes most evident.

It has been found by experience that switches Sometimes stick forvarious causes or do not open wide enough or are not supplied withsufiicient power to actuate them with certainty; for example, when theswitch in the controlled circuit is operated by an electromagnet, as inmy Patent 999,710, the maximum pull is exercised the moment the magnetis energized and if the pull is insufiicient the apparatu'sfails towork. In my present apparatus the circuit through the heating coilremains closed after the moment when the switch in the controlledcircuit is supposed to open, and. the pulling action of the heating coilcontinues. It is obvious that great force may be generated by theheating coil and lever, and consequently by adjusting the contact 15properly almost any amount of pulling force may be obtained. The delayedopening of this electrothermally operated switch 15, 30, therefore,produces a high degree of certainty of operation and there is no dangerof this switch remaining closed too long because when the lamp 41 hasbeen shut oil" long enough to permit the temperature in the bath to dropbelow the prescribed point the mercury in tube 1 will drop and cause thecircuit through the heating coil to be opened whether the switch 15, 30is open or not. The time lag of the opening of switch 15, 30 may,therefore,` be increased to any reasonable extent without endangeringthe operation of the parts as a whole. But even if the mercury tubeshould not open the circuit through the coil 10, said coil would beprotected, for under ordinary adjustment the heat of the coil wouldexpand rod 11 enough to bring the switch 21 out of engagement with thecontact 15 before said coil would be overheated or the insulationthereof damaged.

The heating of coil 10and consequently the movement of the lever 21,continues until either the contactor 30 has left the Contact 15 or themercury in tube 1 has dropped down low enough to leave the needle 6. Assoon as either one or both of these actions has occurred the circuitthrough coil 10 is broken and the rod 11 begins to contract and therebymove the lever again toward closed position. If at the time thecontactor 30 meets the contact 15 the temperature in the bath is abovethe prescribed point and the mercury in the tube is touching the needle6, the coil 10 will again heat and prevent the contactor 31 from closinguntil the temperature in the bath has dropped sufficiently to open thecircuit in the mercury tube.

It will be noted that this apparatus will operate on either direct oralternating current.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is: y

1. A thermal relay comprising a main circuit, a relay circuit, a thermalswitch controlling said relay circuit, and means operated by said relaycircuit for interrupting rst the main circuit and then the relay circuitwith an appreciable lapse of time intervening, whereby the relay circuitremains energized long enough to insure the interruption of the maincircuit and the relay circuit is finally interrupted for its ownprotection.

2. In combination, a main circuit, a. relay circuit, a switch arm inseries in the main circuit, a contact in the main circuit adapted l tobe engaged by said switch arm, an expansion rod adapted to operate saidswitch arm, a heating coil adapted to heat said rod for openingsaidswitch arm, said heating coil being in series with the relay circuit,and a circuit breakerin said relay circuit operated by said switch arm,the parts being so timed that the switch arm in-moving to open positionopens first the main circuit and then the rela-y circuit, whereby theopening of the main circuit is insured and the heating coil in the relaycircuit is protected against overheating.

3. In combination, two parallel electrical circuits, one forming acontrolling circuit and the other a controlled circuit, a t-ranslatingdevice in the controlled circuit, a main switchadapted to open and closeboth of said circuits, a coil in seriesin the co-ntrolling circuitadapted to operate said switch, a thermo responsive `switch also locatedin said controlling circuit, said maint switch, in moving toward closedposition, closing first the controlling circuit and then the controlledcircuit and in moving to open position opening first the controlledcircuit and then the controlling circuit. l

4. The combination with the supply mains of an electric circuit, of twocontacts, a nor-- lmally closed switch arm electrically connected to oneof said mains and when in completely closed position engaging both ofsaid sponsive switch connected to the last-to-beleft-contact and to saidremaining supply main, and an electrically operated device in circuitrelation with said thermo r"esponsive switch and controlled thereby formoving said switch arm to open position.

5. In an electric heater, a controlling circuit, a. controlled circuit,a contact in series in each of said circuits, a main switch common tosaid circuitsl and adapted to be in engagement with both of saidcontacts at the same time, said switch being resilient and adapted toremain in engagement with one of said contacts after it has left theother, a heating element in the controlled circuit, a coil located inthe controlling circuit and arranged to operate the main switch and athermo responsive switch also located in the controlling circuit foropening and closing the same.

6. In an electric heater, a heating circuit provided with a contact, acontrolling circuit also provided with a contact, a resilient switcharm. normally in engagement with both of said contacts, a heatingcoillocated in the controlling circuit and adapted upon being heated tocause the switch arm to leave first the contact in the heater circuitand then the contact in the controlling circuit, and a thermo responsiveswitch in the controlling circuit for opening and closing the same.

7. In a heater, the combination with a heating element and a circuittherefor, of a circuit breaker for breaking the heater cirtherlnostaticswitch arranged to open and close the circuit of said retractor havingsaid -coil connected therein, said thermostatic switch being subjectedto the heat of said heating element.-

8. In combination, a main circuit, a relay circuit, a switch arm inseries with both of said circuits, a main circuit contact adapted to beengaged and disengaged by said arm for closing and opening the maincircuit, a heating coil in series in the relay circuit adapted tooperate said switch arm, and a relay Ycircuit contact, also adapted tobe engaged and disengaged by said switch arm for closing and opening therelay circuit, said coil when heated causing said arm to leave first themain circuit contact and subsequently the relay circuit contact.

9. In combination, a main circuit, a relay circuit,-a switch forcontrolling said circuits, an expansion and contraction rod foroperating said switch, and a heating coil in the relay circuit arrangedto heat said rod, said rod being rectilinear and homogeneous, wherebysaid rod lengthens longitudinally when heated and shortenslongitudinally when cooled, the lengthening of the rod causing theswitch to move toward open position, and said switch in moving towardopen position breaking first the main circuit and then the relaycircuit.

10. In a thermal relay, the combination of a main' circuit, a relaycircuit arranged 1 parallel thereto, a thermo-sensitive device in saidrelay circuit for opening and closing the same, a switch commonto bothof said circuits, a resistance lcoil in said relay circuit and anexpansion and contraction rod heated by said coil and connected to saidswitch for operating the same, said rod being held stationary at one endand at the other end being connected to said switch and beingsubstantially rectilinear and composed of metal of such character thatwhen heated the rod lengthens and when cooled shortens thereby varyingthe length of the rod in accordance with variation in temperature andcausing the operation of the switch, said switch in moving toward openposition breaking the main circuit and th'e relay circuit successively,in the order named with an appreciable lapse of time intervening.

11. In combination, a main circuit having a contact in series therein, aswitch arm in f series with said main circuit and adapted to engage anddisengage said main circuit contact for closing and opening the maincircuit, an expansion rod for operating said switch arm, a relaycircuit, a heating coil in series in said relay circuit, said coil beingadjacent to said rod for heating it and thereby operating said switcharm, a relay contact adapted to be also engaged and disengaged by saidswitch arm for opening and closing the relay circuit, said switch inmoving to open position leaving first the main circuit contact andsubsequently the relay circuit contact whereby the relay circuit mayremain closed for heating the coil until the main circuit has beenbroken but in case the current continues to flow through the heatingcoil after the main circuit has been opened, the relay circuit willfinally be opened and the heating coil thus protected from overheating.

12. In combination, two parallel electrical circuits, one forming acontrolling circuit and the other a controlled circuit, a heater in thecontrolled circuit, a main switch adapted to open and close both of saidcircuits, a coil in series in the controlling circuit adapted to operatesaid switch, said switch in moving toward ope-n position opening firstthe controlled circuit and then the controlling circuit, and a thermoresponsive switch. located in said controlling circuit in position to beinfluenced by the heat of said heater, said thermo responsive switchopening said controlling circuit when heated to a predetermined maximum.

13. In combination, a main circuit having a translating device therein,a relay circuit, an expansion rod, a heating coil in said relay circuitfor heating said rod, and two circuit breakers, one for controlling themain circuit and the other for controlling the relay circuit, said rodbeing mechanically connected to said circuit breakers for actuatingthem, said rod during expansion opening first the circuit breakerwhichcontrols-the main circuit and subsequently the circuit breakerwhich controls the relay circuit.

14. Means for controlling an electric circuit comprising a main circuitto be controlled, a relay circuit, a switch in said relay circuit,electrically operated means in said relay circuit at a point remote fromthe aforesaid switch, said electrically operated means being adapted toopen first the main circuit and subsequently the relay circuit, andadjusting means operative upon said electrically operated means forvarying the period elapsing between the opening of the main and relaycircuits.

v15. In combination, a main circuit having a translating device therein,a relay circuit, an expansion rod, a heating coil in said relay circuitfor heating said rod, two circuit breakers, one for controlling the maincircuit and the other for controlling the relay cuit breaker and therelay circuit circuit circuit, said rod being mechanically conbreaker.

nected to said circuit breakers for actuating In Witness whereof, I havehereunto subthem, said rod during expansion opening scribed my name inthe presence of tWo first the circuit breaker which controls theWitnesses.

main circuit and subsequently the circuit breaker which controls therelay circuit, and THOMAS B' FREAS' means for adjusting said circuitbreakers lVitnesses: for regulating the amount of time elapsing L.WILLARD DECKER, 10 between the opening of the main circuit cir- GENIEVED. DECKER.

